Precast concrete is a construction product produced by casting concrete in a reusable mold or "form" which is then cured in a controlled environment, transported to the construction site and maneuvered into place; examples include precast beams, and wall panels, floors, roofs, and piles. In contrast, cast-in-place concrete is poured into site-specific forms and cured on site.

Recently lightweight expanded polystyrene foam is being used as the cores of precast wall panels, saving weight and increasing thermal insulation.

Precast stone is distinguished from precast concrete by the finer aggregate used in the mixture, so the result approaches the natural product.

Precast concrete is employed in both interior and exterior applications, from highway, bridge, and high-rise projects to parking structures, K-12 schools, warehouses, mixed-use, and industrial building construction. By producing precast concrete in a controlled environment (typically referred to as a precast plant), the precast concrete is afforded the opportunity to properly cure and be closely monitored by plant employees. Using a precast concrete system offers many potential advantages over onsite casting. Precast concrete production can be performed on ground level, which maximizes safety in its casting. There is greater control over material quality and workmanship in a precast plant compared to a construction site. The forms used in a precast plant can be reused hundreds to thousands of times before they have to be replaced, often making it cheaper than onsite casting in terms of cost per unit of formwork.

Precast concrete forming systems for architectural applications differ in size, function, and cost. Precast architectural panels are also used to clad all or part of a building facade or erect free-standing walls for landscaping, soundproofing, and security. In appropriate instances precast products – such as beams for bridges, highways, and parking structure decks – can be prestressed structural elements. Stormwater drainage, water and sewage pipes, and tunnels also make use of precast concrete units.

Precast concrete molds can be made of timber, steel, plastic, rubber, fiberglass, or other synthetic materials, with each giving a unique finish. In addition, many surface finishes for the four precast wall panel types – sandwich, plastered sandwich, inner layer and cladding panels – are available, including those creating the looks of horizontal boards and ashlar stone. Color may be added to the concrete mix, and the proportions and size aggregate also affect the appearance and texture of finished concrete surfaces.

Ancient Roman builders made use of concrete and soon poured the material into moulds to build their complex network of aqueducts, culverts, and tunnels. Modern uses for pre-cast technology include a variety of architectural and structural applications – including individual parts, or even entire building systems.

In the modern world, precast panelled buildings were pioneered in Liverpool, England, in 1905. The process was invented by city engineer John Alexander Brodie. The tram stables at Walton in Liverpool followed in 1906. The idea was not taken up extensively in Britain. However, it was adopted all over the world, particularly in Central and Eastern Europe as well as in Million Programme in Scandinavia.